The invention relates to packages and envelopes for protecting documents or other valuable papers from destruction by exposure to excessive temperatures. More particularly, the invention relates to such packages having a sacrificial ablative material surrounding the documents to be protected. The ablative material functions to absorb heat by an ablative or endothermic chemical reaction, thereby preventing that heat from destroying the documents contained therein.
An example of a prior art fire resistant envelope is illustrated in U.S. Pat. No. 3,066,847 issued Dec. 4, 1962. An object contained in the envelope shown therein is surrounded by relatively thick layers of hydrated material containing water in molecular form and intended to release water vapor into the area around the object protected by the envelope to thereby protect the object from heat.
Another fire resistant receptacle is shown in U.S. Pat. No. 2,492,422 issued Dec. 27, 1949. That patent shows a file cabinet or safe having walls including relatively thick layers of hydrated material such as gypsum. If the file cabinet is subjected to heat, the hydrated material functions to emit water vapor into the receptacle of the file cabinet to protect documents contained therein.
Attention is also directed to U.S. Pat. No. 2,214,172, issued Sept. 10, 1940 and showing a metal foil pouch providing a recloseable hermetically sealed closure and comprised of thin walls consisting of metal foil and fibrous material, the pouch being intented to contain tobacco and the like and to prevent loss of moisture.